A variety of extendable rail systems have been devised to permit extension of one structure in a horizontal direction from a supporting structure. Examples can be found in the drawer art and also in art relating to vehicles permitting extension of storage containers and the like from the interior cavity of such vehicles. Such structures typically include a support structure upon which a guiding structure is mounted. One or more beam structures extend horizontally from the guiding means. These beams may be extended and retracted in a horizontal direction. Usually, wheels or rollers are provided to assist in the horizontal movement of the beams from the support structure and also to support the beams. The outermost beam is usually used to attach a storage container, whether it be a drawer or containers for storing tools and the like. This permits the container to be pulled outward in a horizontal direction from the storage cavity.
An example of an extendable rail system used in a drawer, is found in U.S. Pat. No. 3,203,749 issued on Aug. 31, 1965 to Bullock et al. This patent discloses the use of a lower rail attached to the support structure, an intermediate suspension rail which extends from the support rail for a pre-determined distance and a drawer rail which extend from the suspension rail for a pre-determined distance. The drawer rail supports a drawer.
A similar rail structure is disclosed in U.S. Pat. No. 3,298,768 issued to Vogt on Jan. 17, 1967. In Vogt, a case rail is attached to the framework of the drawer cabinet. This case rail supports an intermediate rail which includes several rollers for rolling within the case rail. The intermediate rail has a second row of rollers which support a drawer rail. The rollers permit the intermediate rail to be extended horizontally from the case rail and the second set of rollers permit the drawer rail to be extended horizontally a further distance with respect to the intermediate rail. A drawer is attached to the drawer rail and may be extended horizontally on this rail system.
U.S Pat. No. 4,705,315 issued to Cherry on Nov. 10, 1987 shows an extendable rail system used in conjunction with the cargo space of a trade van. Cherry provides a frame assembly having two parallel van frames which is attached to the van storage space body. Rollers are provided on the frame assembly and slide rails are provided as intermediate sections having channels for receiving the rollers. The slide rail has a second channel for receiving rollers attached to a container frame to which a container may be attached. In this way, a container may be pulled horizontally from the van cargo space by extending the slide rail along the first set of rollers and the container frame along the second set of rollers to extend the container from the van.
In most of these operations, particularly where a heavy load is to be placed on the container, a three-part rail assembly is preferred. The first rail is attached to the support structure, the second rail is slidable along the first rail and a third rail, slidable along the second rail, is attached to the storage container. Generally rollers are placed between the sliding portions to facilitate horizontal movement. The three-part slide mechanism is generally stronger than a two-part slide mechanism and is preferred where heavy objects are to be placed in the storage container. As well, this configuration permits the container to be moved for a greater horizontal distance as compared to an equivalent two rail system.
The difficulty with the above designs for a drawer rail structure is that if extremely heavy weights are placed in the storage container, the weight on the storage container will generally cause a twisting action to be placed on the wheels causing binding and even breakage of the rollers from the corresponding rail. This may cause complete failure of the rail system.
The structure disclosed in Cherry has the disadvantage of requiring at least two rails to sandwich the rollers therebetween so that the storage container can be properly supported when extended. The distance between adjacent parallel rails is critical and must be close enough to prevent the rollers from twisting out of the rail and yet must not be too close to prevent the rails from binding or rubbing against the rollers as they move along the rail tracks. Furthermore, Cherry provides that the entire weight of the storage container rests solely on the rollers, making it more difficult to roll the rollers when the storage container is being extended or retracted. As well, this weight on the rollers makes it more likely that the rail will twist from the weight of the roller and that the rollers may slip out, causing the storage container to fall.
A further disadvantage of all these prior systems is that they become difficult to open if the support structure and beams are positioned at an angle from the horizontal. With these systems, significant binding will occur as the system is tilted from the horizontal due to the forces of gravity acting laterally on the rollers and other components of the prior systems causing them to bind, preventing or inhibiting proper extension and retraction of the rails. This is a particular problem with rail systems mounted on vehicles which may be stopped on a surface, such as a hill, which is angled from the horizontal.
Accordingly, it is an object of the present invention to provide an extendable rail system designed to take a greater weight load than before. It is a further object of this invention to provide a guiding mechanism to keep the rails generally moving in a linear direction when the beams are extended or retracted.
It is a further object of the invention to provide a brake means to hold the rail assembly at any horizontal position between and including the fully retracted and fully extended positions.
It is a further object of the invention to provide an extendable rail system which operates adequately when angled from a horizontal position.